<!DOCTYPE html>
<html lang="zh-CN">

<head>
    <meta charset="UTF-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        header,
        nav {
            width: 600px;
            height: 50px;
            margin: 0 auto;
            background-color: blue;
            border-radius: 20px;
            text-align: center;
            line-height: 50px;
            margin-bottom: 5px;
        }

        article {

            width: 300px;
            height: 250px;
            background-color: blue;
            border-radius: 20px;
            text-align: center;
            margin-left: 28%;
        }
    </style>
</head>

<body>
    <header>头部标签</header>
    <nav>导航栏标签</nav>
    <article>内容标签</article>
    <section>定义文档某个区域</section>
    <aside>侧边栏标签</aside>
    <footer>尾部标签</footer>
</body>

</html>